updated for version 7.4a.029
Problem:    Can't build with MzScheme on Ubuntu 13.04.
Solution:   Add configure check for the "ffi" library.
Added tag v7-4a-029 for changeset 2b58913e19a5
updated for version 7.4a.030
Problem:    Missing find_win_for_buf(). (toothpik)
Solution:   Add missing changes.
Added tag v7-4a-030 for changeset bc4fb0317465
updated for version 7.4a.031
Problem:    Compiler warnings. (Charles Campbell)
Solution:   Initialize variables even when not needed.
Added tag v7-4a-031 for changeset 839ebe7c1b2f